Means for aircraft flight training



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MEANS FOR AIRCRAFT FLIGHT TRAINING Filed June 18, 1941 10 Sheets-Sheet 10 lrramrin Patented Jan. 10, 1950 VUNITED STATES PATENT ornca MEANS FOR AIRCRAFT FLIGHT TRAINING Richard Carl Dehmei, Los Angelea, Calif.

Application June 18, 1041, Serial No. 398,590

45 Claims. (01. 35-103) My invention relates to means fmacquainting student pilots with the response of aircraft to the movement of its controls and for training pilots to fly "blindly" by the use of instruments alone. It is also the purpose of my invention to train pilots in the orientation and let down procedures used on radio ranges.

In general, the apparatus of my invention comprises flight equipment, a charting device, and orientator equipment. The flight equipment comprises electro-mechanical facilities controlled by an aileron, rudder, elevator, throttle and stabilizer to give the same instrument readings as would be obtained with an actual aircraft in flight. The instruments duplicate the indications of a convention ball bank indicator, rate of turn meter, rate of climb indicator, altimeter, air speed meter, a true direction (gyro) compass, and a magnetic direction compass.

A charting device is provided for tracing the path of the simulated flight over the range.

This equipment is arranged so that the pilot may observe thecharting device or this device may be obscured from his vision. The apparatus is equipped with an intercommunicating telephone circuit so that the attendant or instructor may talk with the student or simulate the transmittal of weather broadcasts or other airway information.

The orientator equipment comprises an automatic signal controlling device operated either manually by the instructor and/or by the electromechanical circuit referred to above. This signal controller transmits signals to the pilot that duplicate those received in an actual aircraft during its flight in any desired radio range. The signals may include a fan marker, Z marker, glide path and/or, landing marker beacon, and station identification as well as the A and N signals. The automatic signal controlling device is so arranged that wind drift may be introduced, and, in addition. the beams of the range may be shifted to reproduce double beams, dog-legs or other irregularities.

The apparatus of the trainer may be regarded as consisting of two assemblies each usable independentiy or in combination with the other. One of the assemblies consists of aircraft controls and associated circuits necessary to reproduce, on a group of instruments, the same readings as would occur on the flight instruments of an actual aircraft subjected to like control manipulation. This is the Instrument flight training assembly. The other assembly comprises facilities for prac- 2 aircraft flying in a radio range. Orientator assembly.

For further details of the invention reference may be made to the drawings wherein- Fig. 1 is a plan view of pseudo aircraft controls and a traversing table with signal and charting equipment according to the present invention.

Fig. 2 is an elevation of the apparatus of Fig. 1 partly in section.

Fig. 3 is a front elevation of the instrument panel of Figs. 1 and 2.

Fig. 4 is a sectional view on line 4-4 of Fig. 3.

Fig. 5 is a sectional view on line iI of Fig. 4.

Fig. 6 is a plan view of the rudder control on line Ol of Fig. 2.

Fig. '7 is a plan view of the "stic control on line 'I-I of Fig. 2.

Fig. 8 is a sectional view on line H of Fig. '7.

Fig. 9 is a sectional view on line !I of Fig. 7.

Fig. 10 is a sectional view of the charting head on line IlllofFig. 1.

Fig. 11 is a sectional view of the pantograph and recording pencil support on line il ll of Fig. 1.

Fig. 12 is a vertical section of the controller in perspective on line lI-ll of Fig. 2.

Fig. 13 is a perspective view looking underneath of the operating arm which flts on top of the controller of Fig. 12.

Fig. 14 is a perspective view of a slider mount for the arm of Fig. 13.

Fig. 15 is a perspective view of the slider for the mount of Fig. 14.

Fig. 16 is a sectional perspective view of an alternative controller element which may be used instead of Fig. 12.

' Fig. 17 is a plan view of Fig. 16.

Fig. 18 is a sectional view on line lO-IO of Figs. 12, 13.

Fig. 19 is an alternative control element for Fig 12.

Fig. 20 is a wiring diagram for the control elements of Fig. 12.

Fig. 21 is a plan view of the arm of Fig. 13 with the contacts in one position.

Fig. 22 is a partial plan view of Fig. 13 with the contacts in another position.

Y Fig. 23 is a sectional view on line 23-23 of Fig. 22.

Fig. 24 is a schematic circuit showing a modified motor control. Y

Fig. 25 is a schematic circuit diagram for the Thisisthe apparatus of this invention. tising in the determination of the position of an 56 Fig. 26 is a schematic circuit diagram for the signaling circuit and controller of this invention.

Fig. 27 is a schematic telephone circuit.

Fig. 28 is a schematic lamp circuit for the flight instruments.

Fig. 29 is a schematic. auxiliary power source.

Fig. 30 is a schematic power source.

Fig. '31 is a schematic coin control circuit.

Fig. 32 is a schematic of a. modified circuit of this invention.

INSTRUMENT FLIGHT TRAINING ASSEMBLY General By reference to Figs. 1, 2 and 3 it may be seen that the Instrument flight training assembly comprises a complement of instruments consisting of meter I depicting airspeed, the combination meter 2 depicting rate of turn of the aircraft and ball stability, the meter 3 depicting rate of climb, the meter 4 depicting altitude, the meter 5 depicting compass course and a clock 6, each mounted on the instrument board 1 positioned in front of the student pilot seated at 9. A stick l0, simulating the conventional aileron-elevator control of aircraft, a rudder H and a stabilizer 60 are mounted on a frame If for operation-by the student pilot. The control |3 simulates the throttle control of an aircraft. Means are provided, Figs. 25 and '32, whereby movement of the controls II), II, l3 and 60 result in indications of the meters I, 2, 3, 4 and 5 as in an actual airplane. Hence the trainer of my invention provides a method and means whereby a student may learn to fly by the use of instruments alone. He may practice blind flying without the hazard and expense of employing actual aircraft. Pilots already experienced in "blind flying may improve their technique by practice on this apparatus.

ORIENTATOR General A conventional radio range transmits the letter A and the letter N in Morse code into adjacent quadrants in such sequence and intensity relationship that these signals overlap along four selected compass hearings to form narrow on-course beams. Lateral deviation from these beams results in predominance of either the A or N signal depending, respectively, on whether the deviation is into a contiguous A or N quadrant. Assuming the deviation from the on-course beam is into an A quadrant the A signal will increase in volme while the N signal becomes weaker. This reduction in N signal strength continues to approximately one-third of the angular width of the quadrant where the signal fades to zero. Thereafter substantially only an A signal is heard and this increases in intensity until the bisector of the quadrant is reached. As the flight is continued across this bisector the A signal starts to decrease in intensity. When the flight has reached a position approximately one-third the quadrant width from the next on-course beam, the N signal again becomes audible and continues becoming louder until it again equals the A signal forming another on-course beam. The areas adjacent to a beam and within which both signals can be heard, one louder than the other, are the bi-signal zones. As indicated above, the width of these bi-signal zones is approximately onethird the width of the respective quadrants. All

signals increase in strength as the center of the radio range is approached. Directly above the in continental code.

Sometimes there is a momentary reduction or fading of the signals, or a false cone of silence, at other points along the airway due to atmospheric or local disturbances. To avoid any uncertainty from this cause as to location of the center of the radio range, many ranges are equipped with a Z type'marker beacon which emits a distinctive signal in the cone of silence. Fan type marker beacons which transmit a fan-shaped radio pattern across the equi-signal zone are often placed 20 miles from the center of the range. The markers around any given radio range station are identified by a succession of single dashes, or by groups of two, three or four dashes to indicate the particular course of the range.

Multiple courses exist at some locations, particularly in mountainous country. That is, the

equi-signal zone, which is normally about 3 in width, may be broken up into a number of narrow on-course bands with a total spread of 10 or 15 or even more. in bent courses. If the aircraft continues in straight flight under these conditions, the range courses seem to be swinging from side to side.

Wind causes drift of aircraft over a range and if of appreciable velocity may in certain conditions of flight lead the pilot to believe he was on a different course of the range than was actually the case.

To identify the particular range in which a flight is conducted, the A and N signal sequence is interrupted after each twelve successive transmittals to project station identifying signals first in the N pair of quadrants and then in the A quadrants. These signals consist of two letters A complete cycle requires 37 seconds. for the twelve A and N transmittals and twelve seconds are utilized for the station code.

Provision is made at most range stations for simultaneously broadcasting voice with the range signals so that weather reports or other information'may be transmitted to the airway.

Inasmuch as like signals are transmitted into opposite quadrants of a range it becomes necessary to identify the quadrant in which the, aircraft is flying. It is also necessary to find a' range course as quickly as possible from known position. This establishment of is referred-to as orientation.

Orientation may be practised on the apparatus of my invention which in this part comprises a pantograph 15, Figs. 1 and 2, mounted on the the unposition fixed pivot 62 in bearing 64, Fig. 11, attached to the traversing table 8 and having a course charting head l4 whose position and movement on the table depict the position andmovement of A related difllculty is found Of this period, 25 seconds are used anew dio range. The effects of wind drift and beam irregularities may be introduced by displacing the signal controller as in the slide rails ll. The automatic regulation of the signals has great usefulness in that it dispels the confusion which has heretofore existed both in the student and his instructor due to the inevitable lag and errors which attend attempts by the instructor to manually vary the signal strengths to conform to the students movement of the charting head ll about the table. In addition the signal controller Ii, because of its automatic operation,-

eliminates the need of the skilled instructor heretofore required for the manual variation of the signal strengths. The freedom from need of such attendant not only provides more satisfactory and economical operation, but makes possible the operation of an orientator from a coin collector switch rendering the orientator operative for a timed interval.

A detailed disclosure of the facilities of my invention now follow. For the sake of brevity, the Instrument flight training assembly and the Orientator assembly will be described in combination, it being clear that either may be used alone. The two assemblies are mechanically linked together for combination use by the ASM motor shaft 62, Figs. 1 and 11 and the SM steering motor shaft 6|, Figs. 1 and 2.

The course charting head ll, Figs. 1, 2 and 10, is steerably mounted in the pantograph ii at the sleeve I8, Fig. 10. The position of the head ll represents the location of the aircraft on the range, the orientation of the head is the true course and the velocity of the head is proportional to the air speed. Mounted in the Joint I, Fig. 1 is a path tracin pencil 51 which plots the course in reduced scale on map I9, Fig. 1. The dash board 1 mounted at the side of the table I, is bisected vertically at 68, Fig. l and Fig. 3, and the section at the left of the partition is hinged at If, Fig. 3. Dropping this hinged section forward exposes the course charting head I4 to the pilot seated at 9. The entire traversing table 8 is exposed to any attendant seated at 29'.

The tractive wheel 85, Fig. 10, is rotated on its own axis 69 by the air speed motor ASM, Fig. 2 and Fig. 1 which is responsive to controls II, II, II and 60 through the circuits, Figs. 25 and 32. Themotor ASM is secured to the underside of the traversing table 8. The ASM motor drives the wheel 55 through the reduction gearing II and 'Il, Fig. 11, the shaft 62, sprocket 12, the chain 13, Fig. 1 and Fig. 2, the driven sprocket 14, Figs. 2 and 10, and the flexible shaft 15 which transmits power through the miter gears 18 to the tractive wheel 65 which moves the head II.

The motor ASM also drives the air speed indicator I through the shaft ll and pulleys ll and II, Figs. 2, 3 and 4. The air speed indicator l is a tachometer of any standard design but calibrated in terms of air speed units. The tachometer construction which I prefer is the revolving magnet type commonly used for automobile speedometers. However, a vibration tachometer, or an electrical tachometer could be used as alternatives.

To simulate turning of the aircraft, the steerable course charting head it is rotated by the steering motor SM, Fig. 1 and Fig. 4, said motor being responsive to controls III, II, I! and II through circuits, Figs. 25 and 32. Mechanical connection between the motor SM and head M is through the gear train 03, Fig. 5, the shaft ii, the miter gears Ill, Fig. 11, the driving sprocket ll, the chain 32, Figs. 1 and 2 and the driven procket 33, Figs. 1, 2 and 10. Directly connected to the motor SM is the rate of turn indicator 5 I. This indicator, like the air speed indicator i, is a tachometer of any conventional design. It is, however, of zero center construction and is calibrated to show the turning rate in "needlewidths. The type of tachometer which I prefer is the revolving magnet design. Contained in the same housing as the rate of turn indicator is the "ball bank indicator which comprises a galvanometer BI, Figs. 3 and 25, responsive to controls It, H, I3 and 60 through the circuits of Figs. 25 and 32.

Attached to the shaft 6 I F s. 1 and 2, is a compass dial 3, Fig. 3. Inasmuch as the ratio of the miter gears l and the sprockets ti and I3 is unity, the compass indicates the heading of the course charting head it. Accordingly, the steering motor SM, which controls the rate of turn indicator 2, also performs an integrating operation in positioning the indicator of compass I. The compass 5 shows either the True heading or the Magnetic heading as desired. It will show True heading on the pointer 35 which coincides with the north of the compass card when the head It is travelling north, or it will show Magnetic heading by the pointer 86, which is offset from the True position by the magnetic deviation. In flight training it is frequently desirable to practice the use of the magnetic compass because this type of direction indicator is commonly employed in aircraft. The magnetic compass, however, is subject to spurious rotation while the aircraft is turning and therefore is useless until straight flight has been resumed. To simulate this uselessness of a magnetic compass during execution of a turn I have rendered the compass dial illegiblewhile the steering motor SM is in operation. The method which I prefer for accomplishing this is to use a semitransparent dial having printing which is legible only by rear illumination as from the Ll lamp 81. This lamp is operated by back contacts on the SML line relay, Fig. 25, which operates the SM motor as described under Circuit description" to follow. If it is desired to use the compass as a gyro compass which functions reliably during turns, the lamp 81 may be continually operated by the switch GS, Fig. 28. (See Circuit description.)

The rate of climb meter 3 is operated by direct connection to the altitude motor ALTM, Figs. 1,

4 and 5 which is responsive to controls Ill, H, II and 6. through the circuits of Figs. 25 and 32. The meter 3 is a tachometer having two-way deflection from zero and calibrated to represent rate of climb. The form of tachometer which I go prefer is the moving magnet type. Also driven by the motor ALTM, through gearing 83, Figs. 4 and 5, is the altimeter I, the indicating element of which is a simple pointer attached to the last gear of train as. Thus the altitude motor, ALTM,

5 also performs an integrating operation in positioning the indicator of altimeter 4.

Means other than tachometers could be employed for indicating airspeed, rate of turn and rate of climb. For example, .it is obvious that 7 galvanometers having suitable scale calibration markings and connection as for instance across the motors ASM, SM or ALTM would serve satisfactorily as airspeed, rate of turn and rate of climb meters. I could also use other means actu- 15 ated by an intermediate circuit such as Figs. 25

and 32 which are responsive I3 and 80. Q

Other instruments of my apparatus, as shown in Figs. 1, 2, 3 and 26, are attenuators ATP! and ATM for adjusting the strength of the radio range signals, a meter RPM Fig. 25 depicting an engine tachometer and comprising a galvanometer shunted across the throttle rheostat Pl, Figs. 2, 3 and 25, duplicate rough air switches RASI and RASZfor actuating a feature of the circuit which causes all instruments to have agitated defiections such as occur with aircraft flying in rough weather. The stabilizer 60 varies the tension on the elevator spring 90, Figs. 1,2 and 7 through the screw and bevel gears 24. An average air speed control P2, Figs. 1 and 25 is provided to adjust the average speed of the airspeed motor ASM to any desired cruising value thereby enabling the student to solve problems at a faster rate as he acquires proficiency. A manual signal divider A2-N2 comprising two potentiometers operated by a common potentiometer enables the instructor seated at 29' to manually vary the intensity of the radio range signals for discussion or instruction purposes. The key SIG permits transferring between the automatic sigto controls", ll,

nal regulator l6 and the manually operated po-,

There is a power switch tentiometers' A2-N2. PS for starting the apparatus, a signal lamp Ll indicating operation of switch PS and limit lamps L8 and L9 indicating overtravel of the pantograph.l5.

In addition to the directly operated controls described above, there also are three auxiliary control units which are important features of my invention. These are the steering control motor SCM panel, Fig. 25, which includes the amps.-

ratus within the broken line BB, the air speed control motor ASCM panel, which includes the apparatus shown within the broken line A-A, and the elevator restoring motor ERM assembly, whichactuates the frame ,of potentiometer P9, the contact spring assemblies ACC and ERCI. The SCM and ASCM panels have as their purpose the introduction of time delay between the operation of the rudder, aileron or elevator controls and the response of the instruments I, 2, 3, 4, 5, and RPM and the course charting head I 4 to the new movement of the pseudo-aircraft. Moreover, these panels also provide means for simulating the appropriate holding of the aircraft in a maneuver such as a properly banked turn with substantially relaxed aileron and rudder as p in actual aircraft. The ERM assembly introduces the restoring characteristic of, aircraft to level flight and makes necessary the holding of control pressure in certain maneuvers such as climbs and glides. Instead of employing the motor ERM for shifting and restorin circuit elements P9, ACC, and ERCI, a dash-pot solenoid may obviously be used. A restoring circuit similar to the ERM assembly of the elevator may also be employed on the aileron to simulate the overbanking tendency in steep turns and the recovery tendency in shallow turns. Also, a comparable restoring circuit may be associated with the rudder to make necessary the continued application of slight rudder pressure during turns if such refinement is desired. r

y A further feature of my invention is the ability to easily provide dual controls in either tandem or side-by-side arrangement to permit an instructor to assist the student in performing any maneuver or in the correction of errors. To provide these dual control facilities it is merely necpilot and instructor seated at 9 and 20 are enclosed by a shroud 92 to obscure the surroundings from the vision. This shroud is amxed to frame I2 8.093.

CIRCUIT OPERATION The oscillator 080, Fig. 26, produces a tone at approximately 1000 cycles per second, which is fed from the 0 terminal through the volume limiting attenuators A'ITI and ATI2 located as 'may be seen in Figs. 1 and 3 at the instructor's and student's positions respectively, through the normal contact 5 of the SIG key, to the complete winding of the potentiometers of the signal controller l6, shown in simplified form at Al and NI, but shown in detail in Fig. 20 and described later; through the slide wire rheostat SIL shown also in Figs. 13, 21, and 22, and back to the oscillator OSC 500 ohm terminal. A path for this tone to-the telephone circuit, Fig. 27, may be traced from the Al potentiometer, slider 91 through the normal contacts 2 of the SIG key to the RNG contact I and the AN contact I (when operated) of the interrupter assembly shown enclosed in broken lines at C, to the RNG contact 3 and over lead 2 to Fig. 27. Likewise a tone path may be traced from the NI potentiometer slider 98, the normal contacts 4 of the SIG key to contact 2 on the AN spring assembly, to the RNG contact 3 Fig. 27. Return tone current from the telephone circuit Fig. 27 is over lead I, to the Al and NI potentiometer windings. The contact assemblies I, RA, TRN, RNG, and AN are operated by cams driven by the INTM motor. The AN contacts interrupt the steady tone from the Al and NI potentiometer arms 91 and 98 respectively into A and N signals respectively and pass this current through the swing spring 99 of the AN contact assembly to the RNG contact I and thence to the No. 2 lead to Fig. 27 and the receiyers 95 and 96. After twelve A and twelve N signals the range contacts RNG operate to transfer the head receiver lead No. 2 from the AN springs to the identification contacts I which interrupt tone received first from potentiometer NI through the make contact 2 of the transfer spring TRN and then from the Al potentiometer through the break contact I of the transfer spring TRN, which thereby transmits the station identification signal formed by the cam operated contacts I first to the N channel and then to the A channel. The stud operated break contact I of the RNG range springs prevents a path from the Al potentiometer arm 91 to the AN contacts while identification signals are being transmitted. This is a feature to prevent keying clicks" which would otherwise occur whenever the Al and NI potentiometer arms 91 and 98 are rotated near to the points where the oscillator connects to the potentiometer windings. With the arms in such position the oscillator output is shunted by a low impedance dur- 76 ing the momentary bridging of the make and and lead 2 to brcakANcontacts I andIeachtimethelever spring II swings.

The RA contacts furnish interrupted ground from the source Fig. 29 to the relay RAI oi the aircraft control circuit. Fig. 25, to operate the rough air" feature of that circuit under control of the switch RASI, Figs. 25, 1 and 3, which is manually operated by the instructor.

When the SIG key is operated, the signals furnished to the telephone circuit of Fig. 2'7 are directly under control oi the manually operated potentiometers A2 and N2, Fig. 26, located at the instructor's position, see Fig. 1.

Fig. 2'! provides a telephone circuit for receivim the range signals and for lntercommunicating between the student and the instructor. Apparatus includes the student's and instructor's telephone sets II and Ihtheir respective STU and INST Jacks, the INTC key and a compensating circuit shown at III.

The INTC key has three positions of operation, namely, normal, locking, and non-locking. With the INTO key in the normal position and the telephone sets in their respective lacks, the transmitters and receivers of the two sets are connected in series with power supply over leads I and I from source III and the two sets are connected in parallel to the range signal interrupter circuit C of Fig. 26 over leads I and 2.

With the INTC key operated to the non-locking position the student's and instructor's sets are connected in series with power from source III furnished over leads I and I for the purposes of intercommunication and the sets are disconnected from the range signal leads I and.2.

With the INTC key in the locking operated position the receivers only oi the two telephone sets are connected across the range signal leads I and 2.

It the instructors set is removed from the INST Jack, the student's set is left connected to leads I, and 2 in serieswith the compensating network III. ,Also lead I is opened by operation of the 'jack INST to reduce current consumption from the power source III.

The automatic signal controller II shown in Figs. 1 and 2 and in Figs. 12 to 23, inclusive, continually varies the relative intensity of the A, N and identification signals to correspond with the position of the psuedo aircraft in the range. The signal controller also furnishes Z and fan marker beacon signals.

The controller consists of two attenuating elements AI and NI and operated by a common shaft III as shown in Fig. 12. This shaft is rotated by the grooved arm III shown in Figs. 13, 21, and 22. Sliding in the groove of this arm is a ball bearing I, Fig. 15, attached to the pantograph II Figs. 1 and 2 by'pin 23, Figs. 1, 15, and 23. Any movement of the course charting head II, Figs. 1 and 2, causes a proportionate movement of pin II and hence a displacement of the slide III, Fig. 14, in the groove of the controller arm III and/or rotation of the arm III. It the head II traverses so that pin 23 moves in a-line directed substantially through the center of the controller shaft II2, the center being indicated at III, Figs. 12, 21, and '22, there will be insuiiicient or no side pressure on the arm of the controller to rotate it the 180 which are n to permit the ball bearing to continue its travel. To provide the required rotation of the arm III in such instances a hunting motor HUM, Fig. 12, is connected to the controller shaft I'I2.. This motor is under This snapping action results from the slide III control or the hunting contacts HUC. F18 21 and 22. These contacts extend along the sides oi the grooved arm III and are oi such length that they may be contacted by the bearing III whenever the bearing is near the center III of the controller shaft III. The bearing III carries negative current from the source Fig. 29 and when it exerts side pressure against either HUC contact, the HURI, Fig. 26, or HURI relay (as the case may be) operates to close its rapective contacts to supply power from source Fig. 30 to the hunting motor HUM which rotates in the direction oi the made HUC contact. Any over-rotation will cause the slide to contact the opposite HUC contact closing its associated relay and operating the motor in a reverse direction. Thus the HUM motor causes the arm III of the controller II to hunt between the HUC contacts. To assure rotation oi the arm III in the event the movement of the pantograph II is so rapid that the arm can not immediately -'iollow, an additional safety make contact II'I, Figs. 21, 23, and 26, is provided on the limit contact LIMCI. The circuit diagram within the broken lines D or Fig. 26 is a schematic oi the controller shown in Figs. 12 and 13. Operation 0! this contact I" by over-travel oi the slide III beyond the controller center III closes the relay HURI causing the motor HUM to rotate the arm III until the slide III snaps away from the LIMCI contact I".

having passed the pivoting center III of the controller arm III. To prevent simultaneous operation of the HURI and HURI relays due to any bridging that may occur between the H00 contacts or slow release of the HURI or HUR2 relays, the energizing current for these relays is furnished through break contacts III and III on the alternate relay. The resistance RI limits the torque of the HUM motor and thereby determines its hunting rate.

If the slide III of the controller II over-travels to reach either end of the arm III, the (break) limit contacts LIMCI, Figs. 21, 22, and 26, and LIMCI operate to release contact I oi the LIM relay, Fig. 26, which removes power from the ASL relay winding Fig. 25. The ASL relay released stops the ASM motor which propels the tractive wheel II Fig. 10 of the pantograph II. The LIM relay released furnishes power through its contacts 2 to the limit lamps LI and LI, Fig. 28, located at the student and instructor's positions respectively, and the LIM relay contact I opens power from source III to the oscillator OSC discontinuing the delivery oi signals.

Attached to the slide III of the controller arm is the spring III, Figs. 14, 21, and 22, which contacts the resistance SIL. This resistance is taper wound to cause rapid increase in signal strength as the center of the arm is approached. The pivot center III of the controller arm III corresponds to the center of the radio range. The winding III of the resistance SIL is terminated just short of the center III of the arm, causing the signal circuit to open near the center and form a cone of silence over the center of the range. It is obvious, of course, that instead of employing the resistance, which I prefer, other attenuating means, such as a variable magnetic coupling between an input and output coil, or variation in the impedance of a series coil, could be used as attenuating means and could be operated by movement of pin is with respect to the center III.

The on-course beams, the bi-signal and pure signal intensity distributions simulating the 818- 11 nals of a radio range are obtained from the AI and NI potentiometers of Fig. 12 and Fig. 20 as follows. Inasmuch as the potentiometers are shown positioned face to face in Fig. 12, the diagram of Fig. 20 shows the connections juxtaposed. the sliders 91 and 98 travelling together as shown in Fig. 20 by solid arrows respectively or by dotted arrows respectively.

The leads I" and 2' of Fig. 20 are the leads I' and 2' within the broken lines D of Fig. 26 and after lead I passing through the attenuating resistor SIL, Fig. 26, and Figs. 21 and 22, they connect to the oscillator OSC. The leads 3' and 4' of, Fig. 20 are the leads 3' and 4' within the broken line D of Fig. 26 and after passing through the key SIG connect to the interrupter shown in broken lines at C. The sectors A and C form the A" signal quadrants of the radio range and the sectors B and D form the N" signal quadrants of a radio range. The points a, b, c, and d correspond to the bearings of the range courses.

' Connection from oscillator lead I' to the potentiometers AI and N I is at the points where the A and N{ signal current is to be a maximum. This is approximately at the bisector of each quadrant or the points it and a: on the AI potentiometer and n and q on the NI potentiometer. Some of the common connections between the AI at III] on Fig. 12. Inasmuch as the bi-signal zones are formed by overlapping of the N signal in the A quadrants, the tone return connections to lead 2' are made in the quadrants adjacent to those having tone input connection from. lead I. These return connections are shown at v, w and u, 2 on the AI potentiometer and at I, m and o, p on the NI potentiometer. The points of 'retum tone connection are at approximately /3 the angular quadrant width from the beam points a, b, c, and d, so as to provide a bi-signal zone in which the fading signal attenuates to inaudibility at about one-third the angular width of the quadrant. At the points a, b, c, and at corresponding coils shown dotted at and NI potentiometers are shown to the bearings of the range courses, the potential of the tone current in both potentiometers must be equal. This may be accomplished by properly proportioning the impedance around the windings of the potentiometers. However, a method which I prefer for establishing potential equality between the corresponding points a, b, c and d on the AI and N I' potentiom'eters respectively is to strap them together. By making the position of these straps adjustable, one signal controller can be employed for duplicating the signal distribution of any of a large number of ranges having diflerent course bearings. In my apparatus I have made the straps adjustable by making them movable elements, two of which are shown at III. To assist in the proper positioning of the elements III, I have indexed the ring IIIato show compass bearings.

With the above potentiometer connections and the resistance SIL it will be seen that as the controller shaft is rotated through 360, a signal pattern will be obtained which duplicates the pattern of actual radio ranges.

While I prefer the use of the simple potentiometers connected in the manner above described forvarying the signals to correspond to those of a radio range, other forms of attenuators may be employed. One of these forms is the modification shown in Figs. 16 and 17. A primary winding P carrying current from the oscillator OSC of Fig. 26. induces a tone in the secondary coil SI or the NI attenuator by magnetic coupling through the poles m and the armature us, the

intensity of the induced tone being dependent on the air gap between the poles H2 and the armature H3. By suitably shaping the poles II2, the signal induced in col] SI may be caused to vary in any desired manner. A similar inductive unit is provided for the AI attenuator. This is positioned with respect to the NI unit so that the points of equal induction to the coils SI and S2 occur at the on course bearings a, b, c, and d, Fig. 1'1. The position of the poles may be made ad- Justable to vary the bearings of the points a, b, c, and d as desired.

Another modification employing inductive attenuator units is shown in Fig. 19. AI and NI are toroidal coils with sliders 91 and 98 contacting the toroidal winding. Tone input from the oscillator isto leads I and 2 as before in Fig. 20, and leads 3' and 4 connect to the interrupter shown within the broken lines C of Fig. 26. Tone is inductively induced in the remaining windings of each toroid respectively, the direction of the winding and the distribution of turns being such as to provide the desired signal distribution. Instead of supplying oscillator current to leads I and 2, this current may be supplied to the primary P. If such primary coils ar employed, the contacts 91 and 98 are prevezted from contacting said primary coils by means of the insulating elements I II.

A support H5, Fig. 12, is provided in which the controller I6 is rotatable. This support is indexed with respect to the ring IIIa so that the degree of rotation of the controller in the support-.can easily be read. Rotation of the controller in the support has the eflect Of rotating the entire radio range with respect to the traversing table, which is a feature that is useful in certain training exercises. However, a still more important feature is made possible by this arrangement, namely, the simulation of bent radio beams and-curvelinear wind drift.

The controller is mounted by support H5 in the guide rails I1, Fig. 1, which permit lateral displacement of the controller, thereby making it possible to shift the position of the pseudo radio double beams, dog-legs, and similar irregularities of the range by shifting the controller in the guide I1 during the pseudo-flight of the trainer. Wind drift may be introduced by continuousmovement (manual or otherwise) of the controller I6 along the guide. Fig. 2 shows a motor I with reduction gear I84 and connecting link I82 for mechanically displacing the controller I6 in the guide rails I1, by means oi cord I 8| Connection from the controller to the associated circuits is by the separable plug I30 and the cable I3I. entire range by rotating the controller in the support II5, one set of guide rails I1 are required to obtain windage in any direction- Fan marker beacon tone isfurnished by oscillator 0802, Fig. 26, and interrupted by the cam operated contacts FM to form fan marker signals which are provided along the on-cours'e beams by connection over leads H6, H1, H8, and H9 to contacts I20, I2I, I22, and I23, respectively, of the controller shown in Figs. 12 and 18. These contacts are movable respectively with each of commutator segment I24 is connected to contact Since it is possible to rotate the is through rheostat P6 over lead 42.

13 I25, and as segment I24 communicates with any of the four adjustable fan marker contacts I26, I2I, I22, or I26, tone corresponding to that marker appears at contact I25 and is connected to I26 when the spring I21 on the slider I65 is opposite the contacts I25 and I26. The distance of the contacts I25 and I26 from the controller center I66 is equivalent to the distance of the simulated fan marker from the center of the radio range. From contact I26 the marker tone is transmitted to the receiving circuit of Fig. 27

, over lead I, where it is superimposed on the receivers. The return path to isover lead 6.

Z marker beacon tone is provided by oscilthe oscillator OSC2 V later 0803, Fig. 26, which is connected over lead INSTRUMENT FLIGHT TRAINING CIRCUIT Referring to Figs. 25 to 31 inclusive, all apparatus included within the broken lines F, Fig. 25 (with the exception of the ball bank indicator BI) is mountedon the frame I2, Fig. 2. All apparatus included within the broken lines G and the lines D, and in addition the BI indicator, Fig. 25, the attenuators ATTI and ATM, the key SIG, the lamps, Fig. 28, the telephone circuit, Fig. 27, the power source, Fig. 30, and the coin control circuit, Fig. 31, are mounted at the traversing table 6, Fig. 2. All other apparatus is mounted in a relay cabinet, not shown. Connections therefrom to the table 6 and frame I2 is by cabling.

Referring to Figs. 1 and 2, the airspeed motor ASM mounted beneath the traversing table 6 operates the airspeed meter I, Fig. 3, to give an indication representing the forward speed of the course charting head I4 which charts the flight path of the pseudo-aircraft under control of the stick III, the rudder II, 'the throttle I3 and the stabilizer 66. Meter l is a tachometer of any form. The preferred form of tachometer is the revolving magnet type commonly employed for automobile speedometers. It is driven by the ASM motor shaft extension 41, the driving pulley 46, belt 49, Fig. 2 and Fig. and driven pulley 50.

Referring to Fig. 25, power is applied to the motor ASM from the source Fig. 30 to lead I62 at the rheostat PI6 which is mounted on the shaft 61 driven by the airspeed control motor ASCM through a high ratio reduction gear 66. From PI6 connection is through rheostat PI6 over lead 6!. Pill is mounted on shaft 46 driven by the steering control motor SCM through the high reduction gear 4I. From PIII connection P6 is operated by the rudder bar II through gearing 46, Fig. 2 and Fig. 6.

From P2 connection is through rheostat Pa operated from the control stick I6 through the elevator gearing 44, Flg. 9 and Fig. '7. P6 introduces resistance in the circuit only when back pressure is applied to the elevator. This provides a small reduction in airspeed immediately when a climb is started as in actual aircraft. From P6 connection is through rheostat P2 which 14 is hand operated through average airspeed dial P2, Fig. 1, and regulates the speed at which the ASM motor rotates with all controls in their normal position as shown in the circuit diagram, Fig. 25. From P2 connection is to the throttle rheostat PI actuated by the throttle control l6, Figs. 1 and 2, through the rack 45, Fig. 2. From PI, connection is to the ASM airspeed motor over lead I66.- The power connection is completed from the ABM motor to the source, Fig. 30, over the lead I64 on closure of the ASL relay. 1nasmuch as rheostats PI, P2, P6, P6, PII, and PII, are each in series with the other and with the ABM motor, a change in adjustment of any one will vary the speed of the motor ASMand the airspeed indicator I, Fig. 1, and also the speed of the course charting head I4. During straight and level flight, these rheostats are in the normal positions shown in Fig. 25, and the ASL relay is operated by power supplied from the source, Fig. 29. through contact I of relay LIM which is operated through the closed limit contacts LIMCI and LIMC2, Fig. 27, Fig. 21, Fig. 22, and Fig. 23 which receive power from the source, Fig. 29, over lead 56 and lead 51.

The altimeter motor ALTM, which drives the rate of climb indicator 3, Fig. 3, and the altimeter 4, does not operate during straight and level flight as this is under control of the relay ALTL which is non-operated through the open ALTC contact I, the shaft 61 of the assembly A, Fig. 25, being in the normal position as shown. Also the RAI relay contact 3 and TC contact controlling the AL'I'L relay is open, the latter due to the cam 64 operated by the throttle I6, Fig. 1, being opened to cruising speed position. Likewise the steering motor SM which drives the rate of turn indicator 2, Fig. 1, and orients the course charting head I4, Fig. 1, is idle, the SML relay controlling this motor being nonoperated through the open SMC contacts due to the shaft 46 and the SMC cam 61 being in normal position. The shaft 46, when operating, is driven through the reduction gearing H by the steering control motor SCM.

Having thus followed the circuit operation through one maneuver. it will be apparent how the circuits may be traced. Accordingly, all leads connecting to respective terminals of the main power source, Fig. 30, will be referred to as IIIl-I and Ill-2. Likewise all leads connecting to the respective terminals of auxiliary power source, Fig. 29, will be referred to as "battery" and ground, these being shown on the drawings by the conventional symbols.

Climbs are performed by back pressure on the elevator control III, Fig. 1, which rotates rheostat P6 to increase resistance in the ASM airspeed motor circuit causing some reduction in the indicated airspeed on meter I, Fig. 3. The back elevator pressure also rotates the supporting frame Ila carrying the shaft Illb, Fig. 9, and the shaft 56 through gearing 44 thus rotating the slide 66 of rheostat P9. Contact I of the ACC spring assembly, Fig. 25, is closed by rotation of cam 6i, Fig. 7, and Fig. 9, mounted on shaft 56 and on closure furnishes ground to the ASCLI relay and through the closed T relay contact 5 and the closed AEC contact I to the ERLI relay. Both of these relays operate by having battery standing on their windings through lim t conta ts ASTC a d ERCI respectively. The ASCLI relay operated closes power to the air speed control motor ASCM through rheostat P6. Increasing back pressure speed as shown by meter I.

15 on the stick III reduces the resistance inserted by P3 and increases the speed of rotation of the ASCM motor and hence the shaft 31 rotates faster. The shaft 31 rotates the cam 33, closing the ALTC contact I which operates .the ALTL relay by competing its battery circuit to ground. The ALTL relay being operated, closes power to the altimeter motor ALTM which is under speed control through rheostat PM. Large angular rotation of shaft 31 due to fast or prolonged operation of the ASCM motor results in low resistance remaining in PM and fast rotation of the altimeter motor ALTM which gives a high rate of climb indication on meter 3 and rapid altitude rise on meter 4.

Since shaft 31 is connected to motor ASCM by a high reduction gear 38 there is a time delay between operation of the control stick I3, Fig. 1, and the rotation of the shaft 31 to the position required to produce the desired response of the rate of climb meter 3 and the reduction in air- Hence the use of the apparatus panel A has provided the time lag between control operation and aircraft response which characterizes real'aircraft.

The ERLI relay operated as above, operates the elevator restoring motor ERM which rotates the frame I31, Figs. 7 and 9, by means of the chain drive I36. Frame I31 carries the winding 83 of rheostat P3 and also the contact springs ACC and ERCI. Rotation of frame I31 is in a direction requiring the application of back elevator pressure to retain any desired amount of movement of the slider 59 with respectto the winding 69 and also to retain a given relation between the contact springs ACC and their operating cam 6|, Fig. 8. Rotation of the motor ERM and the frame I31 continues until the ACC contact I opens due to rotation of the assembly around cam Si by the ERM motor or until contacts I of the ERCI limit assembly are opened by rotation of the ERC I spring assembly around the fixed cam I39. The ERCI contact I opened releases the ERLI relay to stop the ERM motor. Contact 2 ofthe ERCI assembly remains closed, however, to allow operation of the ERL2 relay on release of the back elevator pressure so that the motor ERM may then be operated in the reverse direction. It is to be seen from the foregoing that the effect of the ERM motor in displacing the ACC contact springs is to make the aircraftnose heavy and require continued application of some back elevator pressure to maintain the climb, as in actual flight condition. A constant climbing rate will be held when the back elevator pressure is such that the ACC contacts are all open. The stabilizer 80, which changes the tension on elevator spring 30, Figs. 1 and '7. may be used to maintain'the desired elevator do flection.

Also operated by shaft 31, during back pressure on the elevator control I is the rheostat PI3. The rotation of the ASCM motor to produce the climb has been in a direction to turn the shaft 31 counterclockwise and increase the resistance at PI3. This reduces the speed of the airspeed motor ASM, the indication on'the airspeed meter I and the rate of travel of the course charting head The steering motor SM and the steering control panel B has not operatedduring the maneuver.

reversal of the ASCM and ERM motors respectively. Reversal of theASCM motor drives the shaft-31 clockwise to tend restoration of rheostat PI3 to normal and thereby to raise the ASM airspeed motor rotation to cruising value. This reversed operation of the ASCM motor continues only until the reversed operation of the ERM mofor has rotated frame I31 back sufliciently to again open the ACC contacts which release the ASCMR. ASCL2, ERR and ERL2 relays stopping the ASCM and ERM motors. Rapid relaxation of the elevator control III displaces the .ACC cam 3| sufliciently to allow the ASCM motor to operate a relatively long period, actually long enough to permit the shaft 31 to rotate clockwise enough for the ALTC contacts 2 and 4 to close before the ERM motor has v rate of climb meter 3 will then show a slight dive since the ALTMR and ALTL relays have been operated and have revers'ed'the ALTM motor. The shaft 31 may then be returned to normal by applying slight back elevator pressure to close the ACC contact I and return the-ASCM motor to counterclockwise rotation until zero rate of climb is obtained, which occurs when the ALTC contacts are all open due to the cam 68 being in neutral position. v

The maneuver of diving is accomplished by forward pressure on the elevator control Iii. This closes the ACC contacts 2 and 3, operating the ASCMR, ASCLI, ERR and ERLZ relays which respectively operate the ASCM and ERM motors in the manner as described above. The ASCM motor being operated, rotates the shaft 31 clockwise, reduces resistance from'rheostat PI3 in the ASM airspeed motor circuit causing the airspeed indicator I, and the course charting head It to also have higher response. The shaft 31 rotating cam 33 closes the ALTC contacts 2 and 3 to furnish ground for operation of the ALTMR and ALTL relays, which being closed, operate the ALTM motor in series with rheostat PM to drive therate of climb meter and altimeter in altitude loss. The speed of the altimeter motor ALTM and the airspeed motor ASM depend on the position of the sliders of rheostats PH and PI3 respectively. These slider positions depend in turn on the displacement of shaft 31 which is determined by the speed and length of operation oi the ASCM motor. Large deflection of the elevator control I0 reduces the resistance P9 in the ASCM motor circuit, causing it to rotate shaft 31 through a large angle in relatively short time.

Obviously, the same deflection of shaft 31 (and hence the same dive) may be obtained by smaller deflection of control It with less removal of P3 with the aircraft performing an outside loop as described under Loops.

Recovery from the dive is by relaxation of forward pressure or the exertion of back pressure to hasten the pullout. The ACC contact I closes to operate the ASCLI relay operating the ASCM opened the ACC contacts. The

a direction showing motor counterclockwise through the Pl rheo-' stat and thereby reducing the current to the air speed motor ABM through PIS and slowing the altimeter motor through increased resistance in PM. As the ASCM motor continues counterclockwise rotation, the ALTC contact 'I closes, operating the ALTL relay and the altimeter motor ALTM to show altitude gain.

An inside loop may be performed by continuing greater back pressure on the elevator It than is required to maintain a climb. Initially the back pressure will result in closure of the ACC contact I, operation of the ASCM and ERM motors as described above for climbs. After an interval of Operation, the ERM motor will have rotated the frame I81 which carries the ERCI contacts until they have revolved about the fixed cam I" sufllciently to open the ERCI contact I which removes batter from the winding of relay ERLI releasing the ERLI relay and stopping the ERM motor. Thereafter, only constant or additional back pressure on the elevator control I. will retain the ACC contact I closed and the ABCLI relay operated which will continue operation of the ASCII motor. Shaft 31 will thereby continue rotating in a counterclockwise direction and until it has over-travelled 180 of such rotation, the rheostat PIS will continue to introduce additional resistance in the ABM motor circuit causing a reduction in indicated airspeed on meter l, and the closed ALTC contact I will operate the altimeter motor ALTM to show increasing altitude. Subsequent to passing 180 of rotation, shaft 81 will have rotated cam 68 to close the ALTC contacts 2 and 3 which operate the ALTMR and ALTL relays to reverse the direction of the altimeter motor ALTM, causing it to show decreasing altitude. This reversal point is the top of the loop. Also, after passing the 180 point, the airspeed motor ASM will again receive power and show increased airspeed which is the dive after rounding the top of the loop. The limit contacts ASLC while operated by cam I40 during this complete rotation of shaft 31 will not have released the ABCLI relay to stop the'ASCM motor, as this relay continued to receive battery from the break contacts 63 of the unoperated ER relay.

Recover from the inside loop to normal flight is similar to the recovery from climbs described above. I

Outside loops may be performed by continued forward pressure on the elevator control, the circuit operation being complementary to that described for inside loops. I

Stalls, like an inside loop are performed by continued back elevator pressure. Whether a stall or a loop has been performed is Judged by' the rate of back elevator application.

A normal glide is assumed by closing the throttle ll which operates cam 64 to close the TC contact and operates rheostat PI to insert resistance in the circuit of the airspeed motor ASM, thereby 18 T relay contact I supplies ground for operating the ER]! relay, which prevents operation of the ERR and'ERL2 relays and consequent reversal oi lowering the indicated speed on meter I and re- 4 ducing the rate of travel of the course charting head It. The TC contact, when closed, supplies ground to operate the T relay and thereby the ER-LI relay which starts the elevator restoring motor ERM, which through chain I, Fig, '7, rotates the frame I31, to make necessary the continued application of back pressure on the elevator control It. The T relay contacts I and 3 furnish ground to the ALTMR and ALTL relays, which being operated, start the altimeter motor ALTM in the direction which drives the rate of climb and altitude meters to show altitude loss.

the ERM motor with any relaxation or forward pressure on the elevator control II.

As in climbs, when the ER]! motor has shifted the contact springs ACO after initial operation of the ERLI relay, it is n to hold sufllcient back pressure to avoid closure of the ACC contacts 2 and: ifitisdesiredtoholdtheairspeedmotor ABM at constant speed. Otherwise, closure of these contacts will operate the ABCMR and ASCL2 relays to start the airspeed control motor seem in the diving direction, rotating shaft :1

and rheostats PI! and PM clockwise to a decreased resistance setting, which speeds up the ABM and ALTM motors respectively to show higher airspeed on meter l and faster altitude loss on meters 3 and 4.

Excessive back pressure will cause the ACC contact I to operate and close the ERLI relay throughTrelay contact 5 andAECcontact I until the ERM motor has rotated the frame I31 and limit contacts ERCI so as to open ERCI contact I, interrupting battery to the ERLI relay, releasing that relay and stopping the ERM motor. During this operation, and as long as sumcient back pressure is used to continue the ACC contact I closed, the ABCLI' relay will be operated and allow the ABCM motor and shaft 31 to rotate in the climbing or counter-clockwise direction, adding resistance to the airspeed motor ABM at PI: and to the altimeter motor ALTM at PI2, causing a reduction respectively in airspeed at meter I and in rat of climb and altitude at meters I and 4. Prolonged operation of shaft 31 results in a power-oi!" stall with the same circuit operation as in the case of power stalls described above.

Any desired rate of descent in the glide may be held by adjusting the back elevator pressure to keep the ACC contacts open.

Recovery from the glide or power-of! stall is effected by opening the throttle I3 to open the TC contact removing ground from the '1 relay which releases and thereby opens ground to the ERLI, ALTMR, ALTL and ERX relays. Opening the throttle also operates rheostat PI to reduce its eflective raistance and thereby to partially return speed to the ABM motor and airspeed meter I. To level oi! in recovery, the elevator pressure is relaxed and the return to level flight is as described. under recovery from climbs above.

Maneuvers subsequently to be described involve use of the aileron controls It and the rudder control II. Deflection of the aileron control II rotates gears Ill and "2, Figs. '1 and 9, to operate rheostat P1 and cam' I43 associated with contacts SKC2. Deflection of the aileron also rotates shaft 22, pulley I35, belt I", the driven pulley I, the shaft I" and the gear I" of the differential box I 49. Deflection of the rudder rotates gears ISI, I5I and IR, Fig. 6, which in turn operate rheostat P3 and P4 and cam I53 associated with contacts SKCI. The rudder bar II also rotates shaft I56, Fig. 2, pulley I51, belt I58, driven pulley I59, Fig. 6, shaft I" and gear I6I of the differential box I49. Attached to the gear I62, differentially driven by gears I48 and ISI is rheostat P5 and contact assembly SCC. The belts II! and I5! are so arranged that like movement of the aileron and rudder controls causes opposite rotation of gears Ill and Iii and'therefore rotation of gear I62 to which is connected the slider of rheostat PS and the cam I62 ofthe contact assembly SCC. Equal and opposite deflection of the 1 20 P9 and the ACC contacts in the direction requiring back elevator pressure to hold constant air- Y speed. If back pressure is not held, the ASCM steering motor SM directly to the differentially geared rheostat P by closure of the SK relay contact I. The circuit to the steering motoris completed through the SML line relay contact I which is operated by the SK relay.

Operation of the SML relay places the speed of the steering motor SM directly under control of rheostat P5 which, when not deflected by rotation of the differential gear I62, introduces sufficient resistance in the SM motor circuit so that this motorwill not operate. The adjustment is such, however, that any small displacement of the slider of rheostat P5 decreases the resistance enoughto start this motor. Thereafter the speed of the motor .SM is proportional to the rotation of gear [62 which moves the slider of P5.

Operation of the SK relay places the steering motor reversing relay SMR under control of the SCC contact 2 through SK relay contact 4. With rudder and aileron deflections such that $00 contact 2 is operated, which occurs whenever both controls are deflected to the left or one control is deflected to the left by an amount more than the other is deflected to the right, thesteering motor reversing relay SMR will operate causing the steering motor to show a left turn. The purpose of transferring control of the steering motor from the steering control panel B to the rheostat P5 and contacts SCC directly is to more nearly simulate the rapid response of actual aircraft to these controls when they are oppositely applied. The steering motor SM will be idle when the rudder and aileron are deflected equally in opposite directions because such movement of the controls l0 and II causes equal rotation of the gears I48 and lil in the diiferentlal and therefore no rotation of gear [62 and no deflection of the rheostat arm from its central position. The aircraft will fly in a straight course with such equality of opposite control. However, the operated SK relay contact 3 operates the ER relay and through ER contacts 2 and I, operates the T and ALTPR relays, respectively.

The effect of operation of the ALTPR relay is to reverse the connections of rheostat PM to shift the power supply leads i Ill-2 to the opposite ends of the winding of PM thereby causing less rapid rotation 'of the ALTM motor with increasing rotation of shaft 31 upon operation of the ASCM motor. The ALTM motor driving the rate of climb and altimeter thereby causes these instruments to show altitude loss at a decreasing rate as back elevator pressure is applied.

Operation of the T relay contacts I and 3 operates the ALTMR and ALTL relays, respectively, and thereby the altimeter motor ALTM in a direction to show decreasing altitude. The T relay contact 2 operates the ERLI relay but does not operate the ,ASCLI relay due to the circuit to the ASCLI relay through the AEC contacts being broken at the T relay contact 5. The T relay contact 4 operates the ERX relay to prevent operation of the ERL2 and ERR relays and operation of the ERM motor to a forward elevator position.

The ERLI relay being operated causes the ERM motor to rotate the frame I31 and the winding of motor will operate by closure of-the ACC contacts- 2 and 3 and the ASCM motor energized will rotate shaft 31 and thereby the sliders of rheostats Pitt and P to respectively vary the speeds of the airspeed motor ASM and the altimeter motor ALTM.

Overtravel of the ERM motor is prevented by opening of the ERCI limit switch contact I which releases the ERLI relay and stops the ERM motor.

The lower break contacts of theoperated ER relay are open, hence the ASLC contacts have control of the ASCLI and ASCL2 relays and pre- 4 vent over-travel of shaft 3! beyond approxi mately rotation.

Deflection of the rudder bar displaces the arm of potentiometer P4 with respect to the arm of potentiometer P! by the degree of the side slip. This places potential across the ball indicator Bl which is so polarized as to throw the ball outward.

Recovery from the side slip is by neutralization of the rudder and aileron. The SK relay releases when the SKCI and SKCZcontacts open. The SK relay being released releases the ER relay. The ball indicator returns to neutral as the arms of the potentiometers P4 and P1 are restored to parallel positions.

The ER relay released releases the T relay which releases the ERX and ERLI, ALTMR and. ALTL relays. The ERX and ERLI relays being released allow relaxation of the elevator by re-- turning control of the ERR and ERL2 relays and thereby ERM motor to the ACC contacts. The ER relay in releasing also releases the ALTPR relay, causing restoration of the winding connections of potentiometer PM to normal. The SK relay being released returns control of the SML relay to the SMC contacts.

Turns by use of the aileron and rudder jointly havethe following circuit operation. A left turn is used as an example in the description.

Application of left aileron and left rudder result in a smooth entry to a banked turn when the two controls are coordinated to maintain the ball indicator, BI Fig. 25 (also shown at meter 2, Fig. 3) in it undefiected (or center) position. This occurs when the rudder and aileron deflectionsdisplace the slides of the potentiometers P4 and P1 so that they are at equipotential points. Excessive rudder causes the potential of the P4 slide to exceed that of the P1 slide and the'ball indicator BI swings to the outside of the turn indicating the skid. Insufiicient rudder causes excessive potential at the P1 potentiometer slide and the ball swings to the inside of the turn indicattion of the rudder and aileron controls and the J rotation of shaft 40 to its final position. Since, as will be seen, the final position of shaft 40 determines the rate of turning of the pseudo-aircraft,

its delayed response to the controls simulates the delayed response of actual aircraft to control manipulation. Moreover, the final position of shaft 40 is dependent on the length of time that 

